Centering mechanisms for turbocharger bearings

ABSTRACT

An exemplary assembly includes a turbocharger center housing with a bore; a turbocharger bearing with an annular groove having a diameter; and a substantially planar spring, seated at least partially in the annular groove for positioning the turbocharger bearing in the bore of the housing, where the spring includes a first end and a second end, a free standing inner diameter, a plurality of straight sections tangent to the free standing inner diameter and disposed between the first end and the second end and a curved section disposed between two of the straight sections where the spring balances an inward radial bias with an outward radial bias to reduce contact between the bearing and the housing and variation in a squeeze film thickness. Various exemplary springs, bearings, housings, assemblies, etc., are also disclosed.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/536,710, filed on Aug. 6, 2009, which is incorporated by referenceherein, which is a divisional of U.S. patent application Ser. No.11/281,735, filed on Nov. 16, 2005, which is incorporated by referenceherein.

TECHNICAL FIELD

Subject matter disclosed herein relates generally to turbomachinery forinternal combustion engines and, in particular, bearings and componentsfor use with bearings.

BACKGROUND

Advantages associated with low friction rotor bearings are well known inthe field of turbomachinery where rotor speeds often exceed 100,000 RPM.Such high-speed applications, owing to the fact that rotor imbalanceforce increases as a square function of rotor speed, typically include amechanism for radial damping of the rotor bearing. In addition, changesin operating conditions can generate significant axial thrust forcesthat act on a bearing; these forces should also be damped or absorbed.

One type of low friction bearing is referred to as a fully floatingbearing. Fully floating bearings rely on hydrodynamic films, inparticular, an inner hydrodynamic film or films between the rotor shaftand the bearing and an outer hydrodynamic film or films between thebearing and the housing. Fully floating bearings can spin in thehousing, typically, at between about 20 and about 40 percent of therotor shaft speed. However, floating bearings can become unstable due toresonant frequencies in the shaft/bearing system driven by suchrotation. To prevent such instabilities a semi-floating approach hasbeen used.

In a cylindrical coordinate system, a bearing may be defined withrespect to radial, azimuthal and axial coordinates (e.g., r, Θ, z,respectively). See, e.g., Beyer, W. H., CRC Standard MathematicalTables, 28th ed. Boca Raton, Fla.: CRC Press, p. 212, 1987. Within abearing housing, referred to as housing in subsequent text, asemi-floating bearing is normally located axially and azimuthally viaone or more mechanisms. To prevent rotation (i.e., spinning in Θ), asemi-floating bearing may employ a radial pin locating mechanism. Such amechanism allows some movement in a radial direction along a radial linedefined by the pin but prevents rotation of the bearing in the housing.While such a radial pin may provide for axial positioning as well,thrust forces can cause wear and misalignment issues; hence, othermechanisms are sometimes used for axial positioning (e.g., a pinoriented with its axis parallel to that of the bearing and fit into anotch in the end of the bearing).

Overall, an industry need exists for bearing and bearing componentshousings that allow for better alignment and/or reduced wear. Variousexemplary bearings, bearing components and housings presented hereinaddress such issues.

SUMMARY

An exemplary assembly includes a turbocharger center housing with abore; a turbocharger bearing with an annular groove having a diameter;and a substantially planar spring, seated at least partially in theannular groove for positioning the turbocharger bearing in the bore ofthe housing, where the spring includes a first end and a second end, afree standing inner diameter, a plurality of straight sections tangentto the free standing inner diameter and disposed between the first endand the second end and a curved section disposed between two of thestraight sections where the spring balances an inward radial bias withan outward radial bias to reduce contact between the bearing and thehousing and variation in a squeeze film thickness. Various exemplarysprings, bearings, housings, assemblies, etc., are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the various methods, devices, systems,arrangements, etc., described herein, and equivalents thereof, may behad by reference to the following detailed description when taken inconjunction with the accompanying drawings wherein:

FIG. 1A is an end view of a prior art bearing for a turbocharger.

FIG. 1B is a cross-sectional view of a prior art bearing.

FIG. 1C is a cross-sectional view of a prior art bearing in a prior arthousing.

FIG. 1D is an end view of a prior art bearing in a prior art housing.

FIG. 2 is an end view of an exemplary assembly that includes a bearingpositioned in a housing via an exemplary spring.

FIG. 3 is a cross-sectional view of an exemplary assembly that includesa bearing positioned in a housing via two exemplary springs.

FIG. 4 is a diagram of an exemplary spring, exemplary spring tangs andexemplary bearing features that cooperate with a spring.

FIG. 5 is a diagram of an exemplary spring, exemplary spring tangs andexemplary bearing features that cooperate with a spring.

FIG. 6 is an end view of an exemplary assembly that includes theexemplary spring of FIG. 4.

FIG. 7 is an end view of an exemplary assembly that includes theexemplary spring of FIG. 5.

FIG. 8A is a view of another exemplary spring.

FIG. 8B is a view of yet another exemplary spring.

FIG. 9 is an end view of an exemplary assembly that includes anexemplary spring mechanism and a side view of the exemplary springmechanism.

FIG. 10 is a cross-sectional view of an exemplary assembly that includesa bearing positioned in a housing via two exemplary cylindrical rings.

FIG. 11A is a perspective view of an exemplary cylindrical ring of theassembly of FIG. 10.

FIG. 11B is a cross-sectional view of the exemplary cylindrical ring ofFIG. 11A.

FIG. 12 is a cross-sectional view of an exemplary assembly that includesa bearing positioned in a housing via two exemplary mesh rings.

FIG. 13 is a cross-sectional view of an exemplary assembly that includesa bearing positioned in a housing via exemplary springs that aid inaxial positioning of the bearing in the housing.

DETAILED DESCRIPTION

Various exemplary methods, devices, systems, arrangements, etc.,disclosed herein address issues related to technology associated withturbochargers and are optionally suitable for use with electricallyassisted turbochargers.

For various drawings, a cylindrical coordinate system is used forreference that includes radial (r), axial (x) and azimuthal (Θ)dimensions. FIG. 1A shows an end view of prior art bearing 100, i.e.,viewed in the r-Θ plane, where dashed lines represent various structuralfeatures. FIG. 1A also indicates a cross-section 1B, which identifiesthe cross-section of the view of FIG. 1B.

The bearing 100 includes a central bore 101 and various features thatallow lubricant to flow to and from the bore 101. The bearing 100includes a pair of outer annular grooves or grind reliefs 104, 104′ topromote lubricant flow. The grooves 104, 104′ are referenced to define acenter section 106, a first outer section 110 and a second outer section110′.

The center section 106 of the bearing 100 includes a top opening 108 anda bottom opening 108′. The openings 108, 108′ are disposed axiallybetween the annular grooves 104, 104′. Lubricant typically enters thebearing 100 from the top opening 108 and drains from the bottom opening108′.

Each of the outer sections 110, 110′ includes a respective annularchannel 116, 116′. Each of the annular channels 116, 116′ directslubricant to a plurality of openings 118, 118′. The openings 118, 118′allow lubricant to lubricate inner journals 120, 120′, respectively.Where the bottom opening 108′ resides at about 0°, the openings 118,118′ are positioned at about 45°, 135°, 215° and 305°.

The bearing 100 further includes an end notch 105, which has asemi-circular section defined by a radius. The notch 105 is centered atan angle Θ_(N) (e.g., about 112° as measured from the bottom opening108′.

FIG. 1C shows a cross-sectional view of the prior art bearing 100 in ahousing 160. In this semi-floating bearing system, a radial pin 162helps to position and prevent rotation of the bearing 100. Morespecifically, the pin 162 acts to locate the bearing 100 axially andazimuthally while allowing freedom in the radial direction along theradial line of the pin 162. Axial thrust load along the z-axis causesforce to be transmitted from the bearing 100 to the housing 160 via thepin 162. As the pin allows for radial movement, some small amount ofclearance exists between the outer diameter of the pin 162 and the innerdiameter of the opening 108. Consequently, during operation thrust maycause axial movement of the cartridge with respect to the housing. Suchmovement can contribute to wear and misalignment.

As described herein, lubricant may be oil such as an engine oil. Withrespect to lubricant flow, the housing 160 includes lubricant inlets163, 163′ that direct lubricant toward the channels 116, 116′ of thebearing 100. The housing 160 includes an upper recess that, inconjunction with the bearing 100, forms an upper chamber 164 thattypically fills with lubricant during operation. The housing 160 alsoincludes a lower recess that, in conjunction with the bearing 100, formsa lower chamber 166 adjacent to a lubricant outlet 165 defined by thehousing 160. In such an arrangement, lubricant flows from the inlets163, 163′ to various regions (e.g., channels 116, 116′, chambers 164,166, etc.) and then to the outlet 165. In addition, some small amount oflubricant may exits via small clearances between the ends of the bearing100 and the housing 160. In general, the lower chamber 166 issubstantially isolated from the upper chamber 164 to better directlubricant to the inner journals 120, 120′. To achieve such isolation,the chambers 164, 166 can have any of a variety of shapes, which are notexplicitly shown in FIG. 1C or 1D (see, e.g., conventional centerhousings).

Thus, in the arrangement of FIG. 1C, supplied lubricant flows from theinlets 163, 163′ to the annular channels 116, 116′ to the openings 118,118′ and to the journal surfaces 120, 120′ of the bearing 100. When ashaft is presented, lubricant films are formed between the journalsurfaces 120, 120′ and the outer surface of the shaft where eachlubricant film has a thickness determined by the diameter of arespective journal surface 120, 120′ and an outer diameter of the shaft.

Lubricant films are also formed between the bearing 100 and the housing160. In particular, films f, f′ are formed between the outer sections110, 110′ of the bearing 100 and the bore walls of the housing 160. Thefilms f, f′ act to dampen motion of the bearing 100 in the housing 160.However, damping effectiveness of the films f, f varies as the bearing100 moves in the bore of the housing 160. In particular, the thicknessof the films f, f varies as the bearing moves in the housing 160.Sometimes, the thickness of such films is referred to as the squeezefilm thickness.

FIG. 1D is an end view of the prior art bearing 100 in the prior arthousing 160. As already explained, the radial pin 162 cooperates withthe opening 108. However, given the nature of the pin 162 and theopening 108, a high degree of eccentricity may exist between the housing160 and the bearing 100. Consequently, lubricant films that form betweenthe housing 160 and the bearing 100 may become uneven as the bearingnutates or rests in the housing.

With respect to an at rest state, the weight of the rotor assembly(e.g., turbine, compressor wheel, shaft, etc.) causes the bearing torest against the housing bore at essentially 100% eccentricity. Onlyupon dynamic motion does the bearing “pump up” (i.e., pressurize) thesqueeze films that then move the bearing towards the center of thehousing bore. If this action does not occur correctly, large motion ordamage to the bearing can occur. This problem is particularly importantfor larger turbochargers owing to the manner in which rotor weightscales versus other parameters.

As discussed herein, various exemplary bearings or related components(e.g., springs, housings, etc.) address primarily bearing/housing films(outer hydrodynamic films) as opposed to the aforementionedbearing/shaft films (inner hydrodynamic films).

As mentioned in the Background, other prior art bearings include fullyfloating bearings where the bearing is allowed to spin in the housingbore. Such fully floating bearings can experience similar issues as theaforementioned semi-floating bearings (e.g., eccentric lubricant films).Various exemplary technologies discussed herein introduce one or morepositioning mechanisms that can address various issues associated withprior art semi-floating and fully floating bearings.

Various exemplary technologies presented herein allow for bettercentering of a bearing in a housing and, consequently, formation of amore even bearing/housing film or films. FIG. 2 shows an end view of abearing 200 that relies on an exemplary spring 250 to locate the bearing200 with respect to the housing 260. In this example, a radial locatingpin is not required, hence, the housing 260 does not require featuresassociated with the pin of the housing 160 of FIG. 1B. Thus, the spring250 allows for use of a housing having fewer features.

As indicated by arrows, the spring 250 balances an inward radial biaswith an outward radial bias to position the bearing 200 in the housing260. More specifically, the arrows indicate directions of force exertedby the spring 250 to the bearing 200 and to the housing 260. Such forcesare sometimes referred to herein as radial support forces. Depending onthe nature of the spring 250 (e.g., spring constant, thickness, fixationmechanism, etc.), when used in a turbocharger assembly, it may becapable of substantially centering the bearing 200 in the housing 260even when the turbocharger shaft is at rest.

An exemplary spring optionally provides a low spring rate centeringforce to keep the bearing near the center of the bore of the housingunder the weight of the rotor assembly. Thus, the spring rate may bepurposely kept as low as possible to avoid increasing the overall rotorassembly support stiffness which can have a detrimental impact on shaftmotion characteristics. Further, in this example, dynamic forces cangenerate the hydrodynamic squeeze film to produce the desirable dampingcharacteristics of a standard semi-floating bearing.

In general, the spring 250 acts to maintain a more even film thicknessbetween the bearing 200 and the housing 260 (e.g., through radialsupport forces). Further, spring 250 provides resistance to flow oflubricant. Consider an example that includes two springs 250 positionednear the ends of the bearing 200. In this example, the springs 250hinders axial flow of lubricant from the bearing/housing film. Such amechanism can help prevent undesirable levels of lubricant leakage atthe ends of the bearing. Yet further, the spring 250 can help preventrotation of a bearing (e.g., via frictional forces between the spring(s)and the bearing and frictional forces between the spring(s) and thehousing). Spring 250 is typically preloaded against the bearing and thehousing bore and optionally preloaded with a force sufficient to avoidor reduce contact between the bearing 200 bearing and the housing 260.

FIG. 3 shows a cross-sectional view of an exemplary assembly wherebysprings 250, 250′ position bearing 200 in a bore of a housing 260. Inthis example, the bearing 250 has annular grooves 205, 205′ to seat thesprings 250, 250′, respectively. In this cross-sectional view, thesprings 250, 250′ may be oriented in any of a variety of manner withrespect to the bearing 200 or the housing 260, as indicated by open andshaded circles for the springs 250, 250′.

As shown in FIG. 3, lubricant inlets 263, 263′ open near the channels216, 216′, respectively. A chamber 264 exists along a central section ofthe housing 260; however, in this example, no pin is required and hencethe housing 260 does not include features to accommodate a locating pin.A lower chamber 266 exists along a central section of the housing 260and adjacent a lubricant outlet 265. The bearing 200 does not require,though can benefit from, a bottom opening such as the opening 108′ ofthe bearing 100. The chambers 264, 266 may extend azimuthally but are,in general, only connected by small clearances between the housing 260and the bearing 200. Further, the inlets 263, 263′ and the outlet 265may be located at positions other than those shown in the figures. Ahousing may have fewer or more inlets or outlets.

With respect to the annular channels 216, 216′ and the openings 218,218′ these may differ, for example, as shown in other drawings. Ingeneral, openings exist to allow lubricant to lubricate the journals220, 220′ and thereby form one or more bearing/shaft films.

With respect to dimensions, a specific example uses a spring 250 with adiameter of about 1 mm. In this example, a notch 205 of the bearing 200has an axial length about twice that of the spring diameter (e.g., about2 mm). These particular specifications may be used for a bearing havingan axial length of about 30 mm and an outer diameter of about 14 mm.Such a bearing may have an inner diameter (e.g., central bore 201) ofabout 8.5 mm.

FIG. 4 shows an exemplary spring 450 and various other features. Spring450 is substantially planar, however, a spring may optionally includesat least part of a spiral (e.g., axial displacement or axial span).Spring 450 can be defined, in part, by a free inner diameter (D_(i)) anda free outer diameter (D_(o)). The exemplary spring 450 can be defined,in part, by one or more outer points 452 and one or more inner points454. In the example of FIG. 4, the spring 450 has three inner points atthe free standing inner diameter D_(i) and three outer points at thefree standing outer diameter D_(o). The spring 450 is sometimes referredto herein as a three-lobed spring that has a substantially smoothvariation between inner and outer points (e.g., sinusoid).

In general, when spring 450 is fitted to a bearing the one or more innerpoints contact the bearing. Positioned in a bore of a housing, the oneor more outer points contact the housing. In such an assembly, spring450 biases the bearing toward the axial center of the bore.

Spring 450 optionally includes one or more tangs. Various exemplarytangs are shown. Tangs 462, 462′ are oriented in substantially the samedirection (e.g., perpendicular to a plane defined by the spring 450, inthe plane, etc.). A single tang 464 may be oriented in any of a varietyof manners. Opposing tangs 462, 466 are typically oriented perpendicularto a plane defined by the spring 450 and in opposite directions.

Exemplary bearing features are also shown in FIG. 4. These featurescooperate with one or more of the aforementioned tangs. For example, agroove 207 may include notches 282, 282′ to accept one or more axiallyoriented tang. Of course, a bearing may include only one of the notches282, 282′. In another example, a groove 207 includes a radial notch 292that may accept a radially directed tang. A bearing may include acombination of such notch features, which may be oriented axially,radially or at angles to thereby properly accommodate one or more tangs.

A spring may have a circular, elliptical or rectangular cross section.Further, the shape of the cross-section may be selected to provide adesired stiffness. For example, a rectangular cross-section will haveslightly higher stiffness than a circular cross-section given the samematerial of construction and approximately same cross-sectional area.However, in some instances, a circular cross-section can provide foreasier positioning on a bearing and/or positioning into the bore (e.g.,consider that a circular cross-section may reduce sliding frictioncompared to a square cross-section).

FIG. 5 shows an exemplary spring 550 and various other features. Spring550 is substantially planar, however, a spring may optionally includesat least part of a spiral. Spring 550 can be defined, in part, by a freestanding inner diameter (D_(i)) and a free standing outer diameter(D_(o)). In the example of FIG. 5, spring 550 has four inner points atthe free standing inner diameter D_(i) and four outer points at the freestanding outer diameter D_(o). Spring 550 is sometimes referred toherein as a four-lobed spring that has a substantially smooth variationbetween inner and outer points (e.g., sinusoid). Of course, springs withmore lobes are possible (e.g., 5, 6, etc.).

In general, when spring 550 is fitted to a bearing the one or more innerpoints contact the bearing and one or more outer points contact thehousing. In such an assembly, the exemplary spring 550 biases thebearing toward the axial center of the housing. Spring 550 optionallyincludes one or more tangs, for example, similar to those described withrespect to FIG. 4. Exemplary bearing features are also shown in FIG. 5,which are also similar to those described with reference to FIG. 4.

An exemplary spring may have a shape other than those shown in FIG. 4and FIG. 5 while still retaining the general biasing concept. Ingeneral, the shape allows the spring to bias a bearing within a housingto thereby maintain a more even bearing/housing film thickness(es).

FIG. 6 shows the exemplary spring 450 as part of an assembly thatincludes a bearing 200 and a housing 260. The bearing 200 includes agroove diameter D_(N). In general, the aforementioned free standinginner diameter D_(i) is less than the groove diameter D_(N). When thespring 450 is fitted to the bearing 200, preloading exists whereby thespring 450 biases the bearing 200 away from the walls of the housing.The free standing outer diameter D_(o), of the spring 450 may changeonce the spring 450 is fitted to the bearing 200. Further, the outerdiameter D_(o) may exceed the bore diameter of the housing 260. Thus,the spring 450 may be compressed to fit the bearing 200 and spring 450into the bore of the housing 260.

In this example, the spring 450 includes a tang 464 that is seated in anotch 292 of the bearing 200 whereby the tang 464 and the notch 292prevent the spring 450 from rotating about the bearing 200.

FIG. 7 shows the exemplary spring 550 as part of an exemplary assemblythat includes an exemplary bearing 200 and an exemplary housing 260. Thefeatures of FIG. 7 are similar to those of FIG. 6 except of course thenumber of lobes differs.

FIG. 8A shows another exemplary spring 850 that has a free standinginner diameter D. A gap exists in the spring 850 to facilitateinstallation. Such a spring optionally includes one or more tangs. Thespring 850 includes several straight sections and several curvedsections wherein the straight sections are tangent to D_(i) and wherethe curved sections define a maximum diameter greater than D_(i). Inthis example, the gap exists along a curved section (e.g., approximatelyat the midpoint of a curved section). Also, the three straight sectionsare tangent to the free standing inner diameter at approximately 0°,approximately 120°, and approximately 240°.

FIG. 8B shows yet another exemplary spring 851 that has a free standinginner diameter D_(i). A larger gap exists in the spring 851 that in thespring 850. Ends of the spring 851 are compressed toward the centerduring installation. In this example, characteristics of the ends (e.g.,angle and length) may be adjusted to provide proper biasing of a bearingin a housing. The spring 851 also includes several straight sections andseveral curved sections. In this example, the straight sections aretangent to D, at approximately 0°, approximately 90° and approximately180°

While a spring may have any suitable spring rate, in one example, aspring has a static spring rate of approximately 2 lb/in (0.35 N/mm) toabout 3 lb/in (0.53 N/mm). While a spring may have any suitablecross-section and associated dimension(s), in one example, a spring hasa substantially circular cross-section and a diameter of about 0.036 in(1 mm). In one example, a spring with a static spring rate of about 2.8lb/in (about 0.49 N/mm) and a diameter of about 0.036 in (about 1 mm)exerts a radial force of at least about 37 lb (about 165 N) to resisttorque. Other examples are possible and may depend on features of abearing, a housing, etc., and/or one or more operational conditions(e.g., steady-state operation, transient operation, rotational speed,etc.).

An exemplary spring lies substantially in a plane (i.e., a substantiallyplanar spring) and is suitable for positioning a turbocharger bearing ina housing. Such a spring may include a first end and a second end and afree standing inner diameter. As shown in FIGS. 8A and 8B, such a springmay have a plurality of straight sections tangent to a free standinginner diameter and disposed between a first end and a second end whereinthe straight sections provide an inward radial bias. As shown in FIGS.2, 4, 5, 6, 7, 8A and 8B, a spring typically has one or more curvedsections. For example, in FIGS. 8A and 8B, the springs include at leastone curved section disposed between two of the straight sections toprovide an outward radial bias. Regardless of the number of straightsections and/or curved sections, a spring typically balances an inwardradial bias with an outward radial bias to thereby position a bearing ina housing. Where a free end exists, such an end may provide an outwardradial bias.

In an assembly, an exemplary spring may be seated in a annular groove ornotch. Of course, partial grooves or notches are possible, for example,three separate grooves disposed at approximately 0°, approximately 120°,and approximately 240° may be used to seat the spring 850 of FIG. 8A. Ingeneral, a groove has a diameter or radius that exceeds the freestanding inner diameter or radius of a spring.

An exemplary spring optionally includes one or more tangs. Such a tangor tangs may extend outward from a plane of a spring or lie in a planeof a spring.

FIG. 9 shows an end view and a side view of another exemplary spring 950where the end view shows the spring 950 as part of an assembly thatincludes a bearing 200 and a housing 260. As shown in the side view, thespring 950 includes a ring member 952 that is machined or otherwiseformed to create one or more tabs 956, 956′, 956″. The ring member 952is optionally split to allow for installation on a bearing and/or tobias a bearing. With respect to machining, a rolling die is optionallyused to cut slots into the ring member 952 to thereby form the tabs.

As shown in the end view, the spring 950 is positioned in a groove orend notch 205 of the bearing 200 where the spring has five tabs 956,956′, 956″, 956′″, 956″″. These tabs bias the bearing 200 and thehousing 260 as indicated by force arrows. As with other exemplarysprings discussed herein, material of construction is typically metal oralloy; however, other materials may suffice given constraints associatedwith operating conditions of a turbocharger.

An exemplary spring includes a thin sheet metal ring with formedcantilever tangs to provide spring action. In such an example, wheretangs are formed in alternating directions, the spring is capable ofoperating correctly regardless of orientation. Such a spring can providea “camming action” that resists bearing torque and thereby helpfrictional forces prevent rotation.

FIG. 10 shows an exemplary assembly that includes a bearing 200, ahousing 260 and a pair of exemplary cylindrical rings 1050, 1050′. Thecylindrical rings 1050 provide for centering of the bearing 200 in thehousing 260. In this example, the pair of cylindrical rings 1050, 1050′sit in a pair of annular notches 207, 207′ in the outer sections 210,210′ of the bearing 200. Various features of the housing 260 are thesame or similar to those described with respect to the housing 260 ofFIG. 3.

The cylindrical rings 1050, 1050 may be or include features ofcommercially available tolerance rings (e.g., tolerance rings marketedby Rencol Tolerance Rings, Bristol, UK). Such tolerance rings are oftenmade from spring steel, stainless steel and other specialist springmaterials. A tolerance ring can be a frictional fastener capable ofhandling direct torque transfer, torque slip, axial retention,controlled collapse and radial loading between mating components. Peaksand valleys or waves act as radial springs and may be described by aspring formula: F=kΔr, where F is the force (e.g., N), k is the springrate (e.g., Nm) and Ar is a radial distance by which a wave iscompressed. Peak and valley shapes as well as material of constructionand treatments can alter properties such as spring rate for a particularapplication.

FIG. 11A shows a perspective view of the exemplary cylindrical ring1050. The exemplary cylindrical ring 1050 is split to allow forinstallation. The cylindrical ring 1050 may be manufactured by feeding amaterial to a rotating gear-like mechanism that deforms the material toform ridges and valleys. The material may be metal, alloy or othermaterial. The cylindrical ring 1050 acts to position the bearing 200 inthe housing 260 in a semi-floating manner. The cylindrical ring 1050acts to resist lubricant flow axially toward the ends of the bearing200.

In the example of FIG. 10, the cylindrical rings 1050, 1050′ have adiameter approximately equal to the diameter of the annular notches 207,207′. Overlap may occur whereby a peak sits in a valley; alternatively,a gap may exist once fitted to a bearing.

FIG. 11B shows a cross-sectional view of the exemplary cylindrical ring1050 along the line 11B-11B of FIG. 11A. The cylindrical ring 1050 has aring width WA, a height, a rise profile and a thickness. The dimensionsmay vary to provide a specific clearance between a bearing and a housing(i.e., a bearing/housing clearance). A specific example has a ring widthW_(R) of about 2 mm to about 3 mm. Such an exemplary ring may be fittedto a bearing having a notch width of about 2 mm to about 3 mm.

An assembly may optionally include an exemplary mesh ring fitted to abearing. A mesh ring may be formed of wire where the wire may be metaland/or other material. Commercially available knitted mesh materialssuch as the METEX® (Metex Corporation; New Jersey, USA) knitted meshmaterials may be suitable for use as a mesh ring for a bearing asdescribed herein. For example, METEX® knitted mesh consists of wires ofvarious metals or strands of other materials that have been knitted intoa mesh structure. Structures of compressed knitted metal mesh yield toshock or vibration stresses but resume their original form when theforce is relieved. Thus, a mesh ring may be resilient and capable ofslight expansion for fitting to a bearing and compression for insertingsuch a bearing into the bore of a housing.

FIG. 12 shows the assembly of FIG. 10 where the rings 1050, 1050′ arereplaced with mesh rings 1250, 1250′. An exemplary mesh ring optionallyhas a rectangular cross-section similar to a piston ring suitable foruse with a turbocharger center housing/bearing assembly. Othercross-sections are possible as well (e.g., circular, oval, etc.). Insuch an assembly, a mesh ring can provide support to the bearing andshaft for centering without providing the majority of the stiffness anddamping support. Further, such a ring can resist outward lubricant flow,which as described above, may cause leakage at the ends of ahousing/bearing assembly.

An exemplary assembly optionally includes one or more of the exemplarypositioning mechanisms discussed herein (e.g., springs and cylindricalrings, a spring and a mesh ring, etc.).

Various exemplary positioning mechanisms optionally operate to positiona bearing axially. FIG. 13 shows an exemplary assembly that includes abearing 1300 in the bore of a housing 1360. The bearing 1300 includesvarious features as already discussed such as a bore 1301, channels1316, 1316′, openings 1318-1318″″, etc. The housing 1360 includesvarious features as already discussed such as one or more lubricantinlets 1363, 1363′, one or more lubricant outlets 1365, etc. However,for purposes of axial position, the housing 1360 includes an annularnotch 1365 and an associated annular plate 1395 or plate(s). In thisexample, the spring 1350 is at least partially seated in the notch 1365and retaining mechanism 1395 to thereby limit axial movement of thebearing 1300 in the housing 1360. Shear stress in such an example isacceptable for the spring 1350. Further, the characteristics of thespring 1350′ may differ from some of those of the spring 1350. Forexample, the spring 1350 may optionally have a larger outer diameterthan that of the spring 1350′ or the spring 1350 may be thicker (e.g., alarger gauge) than the spring 1350′. The assembly optionally includesretaining mechanisms at both ends of the bearing and housing assembly.

Although some exemplary methods, devices, systems arrangements, etc.,have been illustrated in the accompanying Drawings and described in theforegoing Detailed Description, it will be understood that the exemplaryembodiments disclosed are not limiting, but are capable of numerousrearrangements, modifications and substitutions without departing fromthe spirit set forth and defined by the following claims.

1. An assembly comprising: a turbocharger center housing that comprisesa bore; a turbocharger bearing wherein the turbocharger bearingcomprises an annular groove having a diameter; and a substantiallyplanar spring, seated at least partially in the annular groove forpositioning the turbocharger bearing in the bore of the housing, whereinthe spring comprises a first end and a second end, a free standing innerdiameter, a plurality of straight sections tangent to the free standinginner diameter and disposed between the first end and the second end toprovide an inward radial bias at one or more respective inner contactpoints between each of the plurality of straight sections and thebearing, and a curved section disposed between two of the straightsections to provide an outward radial bias at one or more outer contactpoints between the curved section and the housing wherein the springbalances the inward radial bias with the outward radial bias to reducecontact between the bearing and the housing and variation in a squeezefilm thickness and wherein the diameter of the annular groove of thebearing exceeds the free standing inner diameter of the spring.
 2. Theassembly of claim 1 wherein the plurality of straight sections comprisethree straight sections.
 3. The assembly of claim 2 further comprisinganother curved section disposed between two of the straight sections toprovide an outward radial bias at one or more outer contact pointsbetween the other curved section and a housing.
 4. The assembly of claim1 wherein from the first end to the second end, the spring comprises afirst curved section, a first straight section, a second curved section,a second straight section, a third curved section, a third straightsection and a fourth curved section.
 5. The assembly of claim 4 whereinthe straight sections comprise straight sections tangent to the freestanding inner diameter to provide an inward radial bias at one or moreouter contact points between the straight sections and the bearing. 6.The assembly of claim 4 wherein the curved sections provide an outwardradial bias at one or more outer contact points between the curvedsections and a housing.
 7. The assembly of claim 4 wherein the threestraight sections are tangent to the free standing inner diameter atapproximately 0°, approximately 120°, and approximately 240°.
 8. Theassembly of claim 4 wherein the three straight sections are tangent tothe free standing inner diameter at approximately 0°, approximately 90°and approximately 180°.
 9. The assembly of claim 1 wherein the springcomprises a free standing outer diameter.
 10. The spring of claim 9wherein the curved section defines in part the free standing outerdiameter.
 11. An assembly comprising: a turbocharger center housing thatcomprises a bore; a turbocharger bearing that comprises an annular endnotch having a diameter; and a substantially planar spring seated atleast partially in the annular end notch for positioning theturbocharger bearing in the bore of the housing wherein the springcomprises a first end and a second end, a free standing inner diameter,a plurality of straight sections tangent to the free standing innerdiameter and disposed between the first end and the second end toprovide an inward radial bias at one or more respective inner contactpoints between each of the plurality of straight sections and thebearing, and a curved section disposed between two of the straightsections to provide an outward radial bias at one or more outer contactpoints between the curved section and the housing wherein the springbalances the inward radial bias with the outward radial bias to reducecontact between the bearing and the housing and variation in a squeezefilm thickness and wherein the diameter of the annular end notch of thebearing exceeds the free standing inner diameter of the spring.
 12. Theassembly of claim 11 wherein the housing comprises an annular end notchfor seating the spring.